Flush toilets for discharging waste by flushing with flush water supplied from a flush water source have been known for some time in which, as noted in Patent Document 1 (Japanese Patent No. 5592617) (Japanese Patent Unexamined Publication No. 2010-255316), for example, a spout port (rim spout port) for spouting water rearward is disposed at one location in an intermediate area in the front-rear direction of a rim on the side of a bowl, or in an area behind same.
In such flush toilets, a water passageway (rim water passageway) by which flush water is supplied from a conduit on the rear side of the bowl is formed inside the rim on one side in the left-right direction of the bowl, and this rim water passageway is formed to follow the shape in the circumferential direction of the rim, passing through the rim close to the front end of the bowl and continuing up to the spout port (rim spout port) on the rim at the other side in the left-right direction.
Also, as set forth in Patent Document 2 (Japanese Patent Unexamined Publication No. 2000-265525) flush toilets are also known in which, in addition to having a spout port (rim spout port) disposed in the front area of the rim on the side of the bowl, the flush water pipe from the bowl rear side flush water source extends in the front-rear direction up to the spout port (rim spout port), and flush water supplied from the flush water source through the flush water pipe to the rim spout port is spouted rearward.
However, in the conventional flush toilet set forth in the above-described Patent Document 1, because the rim water passageway is formed to follow the shape in the circumferential direction of the rim, passing through the rim close to the front end of the bowl and continuing up to the spout port (rim spout port) on the rim at the other side in the left-right direction, the total volumetric space inside the rim water passageway is large, such that the air space not occupied by the flush water in the rim water passageway is also large when water passes through.
Therefore the larger the entire volumetric space of the rim water passageway interior becomes, the longer is the time until the interior of the rim water passageway becomes filled with water, and time is required until a predetermined flow volume of flush water can be supplied from the spout port, which poses the risk of degrade rim spouting efficiency.
Another problem is the increased likelihood of odd sounds caused by the drawing in of air to the rim water passageway when water passes through.
Also, the formation of a rim water passageway close to the front end of the bowl may decrease toilet design freedom relative to the toilet bowl and rim shape, etc.
Similarly, even in the conventional toilet of the above-described Patent Document 2, the extension of a flush water pipe from the flush water source at the rear of the bowl up to the rim port (rim spout port) results in a longer total flush water pipe length, increasing the total volumetric space inside the flush pipe.
The time until flush water passing through the flush water pipe fills the water passageway thus increases, thereby increasing the time until a predetermined flow volume is achieved, leading to the problem of degraded the water spouting efficiency from the spout port (rim spout port). Other problems include an increased tendency to generate odd sounds caused by the drawing in of air to the flush water passageway when flush water passes through, and possibly reduced toilet design freedom for the toilet bowl and rim shape, etc. due to placement of the spout port (rim spout port) in the front region of the rim at the side of the bowl.